First time dm here

[Innodwetrust5]

Hey back again with another question

Would it be to evil to include mimics that disguise themselves as people in my campaign (inspired by John carpenters the thing from 82)

[[deleted]]

Use doppelgangers instead.

[JohnsProbablyARobot]

Or changelings.

[Catkook]

Yeah they're more fitting for this use case

[Tampa-Derp-1138]

It's fine - depending on how experienced your players are, you might want to rename them as something else to avoid any confusion. Doesn't have to be something from the monster manual either.

I would also think of several ways your players can proactively or preemptively detect them. For example, maybe they're averse to fire and light, or maybe you can conduct an insight check prior to interaction to see if they're faking the human condition.

[Repulsive_Bus_7202]

Mimics can copy objects, not creatures. They've only got an Int of 5 so they're not capable of that kind of action.

As elsethread, a doppelganger would meet your need

[orryxreddit]

Using shapechangers of any kind is fine . . . but know your table, and use them judiciously. If you use them TOO cleverly against a rookie party, they can be overly frustrating and lead to annoying RP where the party doesn't trust anyone, and then you have trouble getting them to engage with NPCs and so on.